Thread: Confusing Problem with some Java code from a book - deals with Classes and Constructors

Hello!

I have been trying to figure out exactly what is wrong with the code I copied from an ebook. I have tried everything I can think of and haven't got a clue!
It has to do with my Class Constructor and it isn't making any sense to me because it is just another section of the code where a variable is re-used when it's
public throughout the whole Class.

 
import java.math.*;
import java.util.*;
 
public class PairOfDice {
 
	public int die1; // Number showing on the first die.
	public int die2; // Number showing on the second die .
 
	public PairOfDice() {
		// Constructor. Rolls the dice, so that they initially
		// show some random values .
		roll(); //Call the roll() method to roll the dice.
}
	public PairOfDice(int val1, int val2) {
		// Constructor. Creates a pair of dice that
		// are initially showing the values val1 and val2.
		die1 = val1; // Assign specified values
		die2 = val2; // to the instance variables.
		}
 
	public void roll() {
		// Roll the dice by setting each of the dice to be
		// a random number between 1 and 6.
		die1 = (int)(Math.random()∗6) + 1; //These variables are giving me 
		die2 = (int)(Math.random()∗6) + 1; // the following error below
//Multiple markers at this line
//	- Syntax error on token "Invalid Character", invalid 
//	 AssignmentOperator
//	- The left-hand side of an assignment must be a variable
 
 
 } // end class Pair Of Dice package;
}
 
public class RollTwoPair {
 
	/**
	 * @param args
	 */
 
	public static void main(String[] args) {
 
		PairOfDice firstDice; // Refers to the first pair of dice.
		firstDice = new PairOfDice();
 
		PairOfDice secondDice; // Refers to the second pair of dice.
		secondDice = new PairOfDice();
 
		int countRolls; // Counts how many times the two pairs of
		// dice have been rolled.
 
		int total1; // Total showing on first pair of dice.
 
		int total2; // Total showing on second pair of dice.
 
		countRolls = 0;
 
		do { // Roll the two pairs of dice until totals are the same.
 
			firstDice.roll(); // Roll the first pair of dice.
			total1 = firstDice.die1 + firstDice.die2; // Get total.
			System.out.println( " F i r s t pair comes up " + total1);
			secondDice.roll(); // Roll the second pair of dice.
			total2 = secondDice.die1 + secondDice.die2; // Get total.
			System.out.println( " Second pair comes up " + total2);
			countRolls++; // Count this roll .
			System.out.println(); // Blank line.
		} while (total1 != total2);
 
		System.out.println( " It took " + countRolls + " rolls until the totals were the same. " );
	} // end main ()
  } // end class RollTwoPairs.

Originally Posted by Norm

Please explain. If there are error messages, copy the full text and paste it here.

Multiple markers at this line
- Syntax error on token "Invalid Character", invalid
AssignmentOperator
- The left-hand side of an assignment must be a variable

Sorry Norm I posted the error message in the code in the PairOfDice section of code.
Please let me know if I posted incorrectly. Thank you for such a quick response!

OK! I finally got it to work but I don't understand why it made a difference.

I changed the way the public integers were calculated in the PairOfDice section to:

die1 = (int) (6 * Math.random()) + 1;
die2 = (int) (6 * Math.random()) + 1;

Instead of:

die1 = (int)(Math.random()∗6) + 1;
die2 = (int)(Math.random()∗6) + 1;

I have no idea why it didn't like the other way as it is almost exactly the same.

Thank you Norm for your suggestions. I guess it's just one of those compiler problems that seem to crop up and bite you when you least expect it.

Originally Posted by Norm

Look at the code in post#1. Could your keyboard have entered a different character for the *?
The forum's formatting code has put in &# 8727 (no space) where you must have thought you had a *

The coding in the post is an HTML version of the * sign. I just looked it up. I am guessing that the software for
this site got confused when looking at all of it crunched up without any space. As I intimated previously every new
version of a compiler has its own peculiarities.

8727 is the unicode character 'asterisk operator'. Java multiplication uses the ASCII character corresponding to unicode 0042.

Visual appearance and the unicode name notwithstanding they are different characters.